Infra-red emitting decoy flare

ABSTRACT

An infra-red emitting decoy flare capable of diverting an incoming missile equipped with a counter-countermeasures system away from an intended target consisting of a primer flare ( 2 ), a spectral flare ( 4 ) and a means for igniting the primer flare ( 22, 30 ), all contained within a flare casing ( 6 ). The primer flare ( 2 ) is formed from a fast burning pyrotechnic composition and is adapted to produce an intense infra-red source of short duration on ignition. The spectral flare ( 4 ) is ignited by the burning of the primer flare ( 2 ) and is adapted to produce a slower burning composition having a fixed ratio in the intensity of infra-red radiation emitted, when burning, in at least two fixed bands.

[0001] This invention relates to an infra-red (IR) emitting decoy flarecapable of being launched from a target to divert a missile equippedwith an IR seeker system away from that target, and particularly to anIR emitting decoy flare capable of diverting a missile having a seekeroperating with a counter-countermeasures (CCM) system using a spectraldiscriminator.

[0002] Most infra-red seeker systems operate in a certain wavelengthrange, or band, of the infra-red spectrum. In this band, the radiatedenergy from non natural sources is generally easy to detect and the hotcomponents of aircraft exhausts or tank engines, for example, radiatestrongly, enabling targets to be easily identified and located.

[0003] Known decoy flares conventionally comprise pyrotechniccompositions bound together with an organic binder and pressed to formpellets. When an incoming missile is detected a pellet is launched fromthe target and ignited. The pellet burns over its surface to produce anintense infra-red source in this band, which can lure the infra-redseeker system of the missile away from the target.

[0004] UK patent application GB 2,300,035 describes an infra-red decoyflare which is formed from a pyrotechnic composition which burns to emitinfra-red radiation. The composition is formed into a plurality ofdifferent blocks with different volumes and different surface areas soas to have different rates of burning. Ignition of all the blocksproduces an infra-red source which is intense enough to cause themissile to lock onto the flare. After a short time the aircraft will beoutside of the field of view of the missile and some of the fast burningblocks will burn completely away. The flare will then radiatecomparatively weak radiation for a time in order to complete thediversion of the missile.

[0005] However, advances in missile seeker systems and CCM systems haveled to seeker systems being able to recognise a decoy flare and ignoreit. Some advanced seeker systems are equipped with CCM systems thatcompare the ratio of the intensity of IR radiation in one band with theintensity of IR radiation in another band of the IR spectrum. Due to thetemperature difference between a conventional flare and the radiatingparts of a typical target and the corresponding different ‘grey body’radiation spectrums, the CCM system can identify and disregard theflare.

[0006] It is therefore an object of the invention to provide a decoyflare which alleviates at least some of the aforementioned disadvantagesand which is capable of diverting a missile equipped with an infra-redseeker system and a spectral counter-countermeasures system away fromits intended target.

[0007] Thus according to the present invention there is provided aninfra-red emitting decoy flare comprising a flare casing, twopyrotechnic components housed within the flare casing and an ignitionmeans for igniting the pyrotechnic components characterised in that thetwo pyrotechnic components comprise a primer flare and a spectral flarewherein the primer flare consists of at least one primer pellet, eachprimer pellet being composed of a fast burning pyrotechnic compositionand being adapted such that, in use, ignition of one primer pelletcauses rapid ignition of all the primer pellets to produce an intenseinfra-red source, wherein the spectral flare consists of at least onespectral pellet, each spectral pellet being of a pyrotechnic compositionadapted such that, in use, ignition of the spectral pellets produces aspectral infra-red source wherein the ratio of the intensity of theinfra-red. spectrum at at least two fixed bands is within a fixed range,and wherein the primer flare and spectral flare are adapted such that,in use, the spectral flare is still burning after the primer flare hasfinished burning.

[0008] In use, the ignition of the primer flare creates an intense IRsource of short duration. The sudden increase in energy can trigger amissile's CCM system. Due to the short duration of burning of the primerflare however, by the time the missile's CCM system is active the primerflare will have stopped burning but the spectral flare will still beburning. The spectral flare has pre-set ratios of intensity betweendifferent bands of the IR spectrum and therefore appears to themissile's CCM system to have the intensity ratios that an intendedtarget would have. Indeed, due to the varying aspects that a target maypresent to a missile seeker and the fact that the ratio of intensitiesof the different bands alters when viewing a target from a differentangle, say an aircraft head on as oppose from the rear, the spectralflare may be judged by the missile seeker and CCM system to be moretarget like, in terms of the required ratio of intensities at differentbands, than the actual target itself.

[0009] Preferably the spectral flare is adapted such that at the fixedbands of the IR spectrum the flare is more intense than the intendedtarget. The spectral flare will then be the most intense IR source withthe correct spectral characteristics. Further, the very intenseradiation from the primer flare can saturate some missiles seekersystems. This would not only cause a missile to activate its spectralCCM system but could also cause automatic brightness compensators tocome into operation. After the primer flare has stopped burning theautomatic compensators will start to reduce to their previous levels.However, if the intensity of the spectral flare in the bands measured bythe missile is greater than that of the intended target then theintensity compensators of the missile seeker may not reduce to a levelthat would include the target. Therefore the spectral flare will be theonly object with the correct spectral characteristics in the field ofview of the missile.

[0010] Also, on initial ejection the primer pellet lights up and burnsextremely quickly. Thus the flare will still be close to the target onignition and energy from the burning flare will be reflected from thesurface of the target. This can increase the radiation seen by themissile's seeker system. Further, the radiation reflected from thetarget can cause the target to appear to be flare like to the seekersystem thus prompting the missile to actually ignore the target.

[0011] In order to achieve a fast burn rate the primer pellets arepreferably discs and the primer flare consists of a stack of said discs.By dividing the primer flare into discs the surface area available forburning is increased over that of a single pellet of the same dimensionsas the stack. The burn rate is therefore correspondingly increased. Thediscs are also preferably provided with a central hole which againincreases the burn rate, but also aids in rapid ignition of the primerflare by allowing the passage of hot particles through the stack.Alternatively a single primer pellet is used and is provided withplurality of holes through the pellet. This again increases the surfacearea for burning and increases the burn rate. Another means ofincreasing the burn rate is providing the primer pellet or pellets withdeep grooves to create more burning surface area. Other arrangements forthe primer pellet will be readily apparent to the skilled addressee.

[0012] A fast burn time is required so that the primer flare hasfinished burning by the time that the seeker system has adjusted. Theburn time of the primer flare is therefore preferably between 100-600ms, more preferably between 150-250 ms. Too short a burn time howevercan reduce the efficiency of the primer flare as there would beinsufficient time for efficient combustion processes to occur.

[0013] The primer flare is conveniently comprised of a composition of anoxidisable metallic material, an oxidising halogenated polymericmaterial and an organic binder. Suitable metallic fuels are well knownin the art and include magnesium, aluminium, alloys of magnesium oraluminium, titanium, boron and zirconium. Preferable the oxidisablemetallic material is magnesium. When ignited magnesium undergoes anenergetic and vigorous exothermic reaction with halogenated polymers andtherefore is particularly suitable for the heat and speed of combustionrequired.

[0014] Similarly the oxidising halogenated polymeric material used inpreferred compositions for the primer flare is a fluorinated polymerbecause fluorine is a better oxidising agent than other halogens andtherefore will react more vigorously and create a more intense IRsource. Suitable fluorinated polymers include polytetrafluoroethylene(Teflon (™) or PTFE) and its copolymers with perfluoropropylene,polytrifluorochloroethylene, copolymers of trifluoroethylene withvinylidene fluoride, homopolymers of perfluoropropylene and copolymersof perfluoropropylene with vinylidene fluoride, homopolymers ofhexafluoropropylene and copolymers of hexafluoropropylene withvinylidene fluoride. PTFE is particularly suitable as it has a highpercentage of fluorine in it.

[0015] Suitable organic binders are well known in the art and includepolyvinylchloride, straight chain chlorinated paraffins such asAlloprene (™) or Cereclors (™) and the tripolymer of vinylidenefluoride, hexafluoropropylene and tetrafluoroethylene. Fluorinatedorganic binders are advantageous in that the binder, also being anoxidising agent, will join in the reaction. A preferred binder is acopolymer of vinylidene fluoride and hexafluoroethylene, for exampleVITON A (™), which coats and binds the constituents very well as well asadding to the reaction.

[0016] A preferred composition for the primer flare is therefore amagnesium-Teflon-Viton (MTV) composition. The ratio of the constituentswill be chosen so that there is the smallest amount of unreactedmaterial after combustion, allowing for the amount of atmospheric oxygenpresent that will join in the reaction in a particular flareapplication. The ratio of the constituents will be easily determined bythe skilled person.

[0017] As the spectral flare needs to have a longer burn time than theprimer flare the spectral flare may usefully be formed from a singlepellet. The spectral pellet can therefore burn relatively slowly andconsistently.

[0018] In order to ensure that the intensity of the spectral flare isbright enough the spectral pellet may be provided with a central holethrough the pellet. The hole will not only increase the intensity of theradiation from the spectral pellet by providing an internal burningsurface but with also ensure consistency of the radiation. As theintensity of the flare is related to the surface area of the burningpellet, a pellet burning from the outside only will slowly drop inintensity as the surface area of burning decreases. Having a centralhole, however, means that as the outside surface area of burningdecreases, the internal burning surface increases, resulting in arelatively consistent burn, increasing the viability of a flare to bemistaken as the target by the missile system. A central hole will alsoaid in rapid and consistent ignition of the whole of the spectral flare.

[0019] Conveniently the spectral flare and primer flare may be adaptedsuch that, in use, the spectral flare is ignited by the burning of theprimer flare.

[0020] The spectral pellet may advantageously be formed to producequantities of hot gas. Conveniently the spectral pellet may be formedfrom an organic fuel, an oxidant and a binder. Organic fuels decomposeto produce gases such as carbon dioxide which can be similar to theelements produced by an aircraft engine say. Thus use of an organic fuelcan provide the required spectral characteristics. Suitable fuelsinclude organic compounds such as sucrose, lactose or starch and alsocompounds such as potassium benzoate. As an alternative to organic fuelsthe spectral pellet may be formed from a boron fuel with a suitableoxidant and binder.

[0021] Suitable oxidants include potassium perchlorate, potassiumnitrate, sodium nitrate or ammonium nitrate. Suitable binders includeViton A, dextrin or polybutyl rubber although organic binders arepreferred as again they decompose into relevant gasses thus binders suchas Viton A or GAP are preferred. Particularly advantageously howeverexplosive materials with a waxy composition may be used as binders. Suchexplosives will be able to function as binders due to their consistencyand will add to the energetic reaction on ignition. Suitable explosivesinclude RDX, HMX and HNS and can also add to the hot gasses produced bythe fuel and oxidant. Other oxidants and binders may be used however andcould be easily determined by the skilled person.

[0022] One advantageous spectral composition comprise approximately 30%by weight potassium benzoate, 65% by weight potassium perchlorate and 5%by weight of binder, say Viton A or RDX.

[0023] Another advantageous spectral composition has, excluding binder,approximately 30% by mass of boron and 70% by mass of potassium nitrate,with Viton A as a binder in a sufficient amount as could be easilydetermined by one skilled in the art. The composition may also includeother materials to enhance the spectral effect, Another advantageouscomposition has, again excluding binder, 20% by mass of boron fuel with70% potassium nitrate and 10% by mass of silicon.

[0024] In some instances it will be beneficial that the primer flareburn with some visible component or without a spectral characteristic,say when utilising reflection from the target surface. However, in othercircumstances it would be advantageous that the primer flare also burnwith a spectral component. In such instances the primer flare maycomprise a fast burning spectral composition. The actual compositioncould be the same as could be used or the spectral pellet but to ensurea fast light up and generation of sufficient energy grooves or aplurality of discs would be used and smaller particle sizes would beused as is well understood in the art. Explosive binders wouldpreferably be used to add to the intensity produced by the primerpellet.

[0025] Further advantages and embodiments of the invention will now bedescribed by reference to the accompanying drawing in which:

[0026]FIG. 1 shows a decoy flare according to an embodiment of theinvention,

[0027]FIG. 2 shows the spectral and primer flares used in a decoy shownin FIG. 1,

[0028]FIG. 3 shows the IR intensity against time for a decoy flare suchas shown in FIG. 1,

[0029]FIG. 4 shows a primer flare pellet according to an alternativeembodiment of the invention,

[0030]FIG. 5 shows a primer flare pellet of a further embodiment of thepresent invention.

[0031] Referring to FIG. 1 a primer flare 2 and a spectral flare 4 arehoused in an open ended cylindrical flare casing 6. The spectral flareis made up of a single cylindrical spectral pellet 10 housed at theclosed end of the casing whereas the primer flare 2 comprises a stack ofprimer pellet discs 8 located next to the open end. Each of the primerpellets discs 8 and the spectral pellet 10 are provided with a centralhole, 12 & 14 respectively, extending throughout the pellets.

[0032] The open end of the casing 6 is sealed by a plug 16, the plugbeing secured by crimping the rim 18 of the casing 6 into a groove 24 inthe plug 16. An expulsion charge 20 is located in a recess in theoutside face of the plug, as is a primary ignition charge 22.

[0033] In use, expulsion charge 20 and primary ignition charge 22 areignited, for example by conventional electric igniters (not shown) inthe flare tube of the target. The expulsion charge 20 is formed from apropellant compositions such as a gunpowder or nitrocellulosecomposition and on ignition generates a large volume of gas whichprojects the flare from the flare tube (not shown).

[0034] Once clear of the flare tube, spring 26 is released and allowsthe ignition stimulus from primary ignition charge 22 to travel down thechannel 28 and ignite the secondary ignition charge 30. Should the flarecasing 6 become jammed in the flare tube, spring 26 is prevented fromrelease and therefore stops the propagation of the ignition stimulus,thereby preventing ignition of the flare in the flare tube.

[0035] Ignition of the secondary ignition charge 30 provides a source ofignition for the primer flare 2. The outer and inner surfaces of theprimer flare 2 and spectral flare 4 are also coated in a primer paste tofurther aid ignition. Further, the primer flare 2, and also the spectralflare 4, are wrapped in aluminium foil 32 and 34 respectively, with bothflares being then wrapped together in aluminium foil 38. The aluminiumfoil aids the ignition of the primer flare 2 and spectral flare 4 byinitially confining the ignition gases thus increasing the initialpressure and thereby aiding the speed and reliability of the ignitionstimulus. Wrapping the pellets in aluminium foil also helps to protectthe pellets during storage. The high temperature generated duringburning of the primer flare 2 may additionally cause the aluminium foilto combust, adding to the radiation from the primer flare 2.

[0036] Ignition of the primed surfaces of the primer flare 2 cause theprimer flare to be very rapidly ignited over all of its outer surface.Hot particles and combustion gases also travel down the central hole 12igniting the inner surface and the faces between the primer pellet discs8. This is aided by the confining effect of the aluminium foil 32.

[0037] The primer pellet discs 8, shown more clearly in FIG. 2; areformed from a fast burning composition such as a composition of MTV.Such a composition creates an intense source of IR radiation having afast burn rate and reaches temperatures of 1900° C.

[0038] The burn rate of the primer flare is also determined by thethickness of the primer pellet discs 8. For an MTV primer pelletcomposition where the discs are of 47 mm diameter and have a centralhole of 6 mm diameter, a stack of 4 to 8 discs of thickness 5-10 mm givethe desired burn rates.

[0039] Alternatively the primer pellet could be formed from a similarstack of discs formed from a composition of potassium benzoate andpotassium perchlorate of small particle size and RDX as a binder.

[0040] Referring back to FIG. 1, ignition of the primer flare 2 causesignition of the spectral flare 4 which is wrapped in aluminium foil 34.Spacers 36 are located between the primer flare 2 and the spectral flare4. This allows for hot particles produced from the burning of the primerflare 2 to ignite the spectral flare over its surface. The spacers 36also help prevent premature ignition due to friction during launch ortransit.

[0041] In an alternative embodiment (not shown) an ignition transfermedium, such as an MTV cord, could be located next to the secondaryignition charge 30 and run through the hole 12 in the primer flare 2 andthe hole 14 of the spectral flare 4. Ignition of the secondary ignitioncharge 30 could then ignite the ignition transfer medium which wouldburn down its length igniting the interior surfaces of the primer flare2 and the spectral flare 4 in turn.

[0042] The spectral pellet, also shown in FIG. 2, is formed from asingle cylindrical pellet. The composition may conveniently be apotassium benzoate, potassium perchlorate and Viton A mix. Potassiumbenzoate comprises 30% by mass of the spectral pellet with 65% potassiumperchlorate and Viton A making up the rest of the pellet. The fuel andoxidant have particle sizes of less then 60 microns.

[0043] Alternatively the spectral pellet can be formed from a boron,potassium nitrate, Viton A mix. The potassium nitrate is 70% by mass ofthe composition and has a typical particle size of 100 μm. The boron isamorphous and sub-micron size and makes up 30% by mass of thecomposition or 20% by mass if an additive like silicon is used. If used,the silicon particles are around 10 μm in size. Boron, potassium nitrateand Viton A gives a hard composition which may be easily cast into therequired pellet shapes. Use of a binder such as polybutyl rubber wouldlead to a more flexible composition which could, for example, beextruded.

[0044] As the spectral flare 4 is formed from a single cylinder the burnrate is much slower than that of the primer flare 2 and due to thecentral hole 14, the intensity of the spectral flare 4 is substantiallyconstant throughout the duration of burning.

[0045]FIG. 3 shows a plot of the IR intensity against time for a decoyflare as shown in FIG. 1 for two fixed IR bands. The primer flare was 47mm in diameter and 40 mm in length, consisting of 8 discs, each 5 mmthick, formed from an MTV composition. The spectral flare was a singlepellet of a potassium benzoate, potassium perchlorate, Viton A mix andwas 47 mm in diameter and was 110 mm in length. Both the primer flareand the spectral flare were provided with a central hole 6 mm indiameter.

[0046] It can be seen that as the primer flare ignites there is a rapidincrease in intensity to a very intense peak which rapidly drops awayagain. The duration of burning of the primer flare can be seen to be inthe region of 200 ms. It can also be seen that one IR band is very muchmore intense than the other. This is the situation with conventionalflares but not with targets such as aircraft. After the primer flare hasfinished burning it can be seen that the spectral flare is alreadyburning and that the intensity of both bands drop off to a lower level.However, the band which was, during burning of the primer flare, oflower intensity is now of greater intensity, which is the oppositesituation to what would be expected for a conventional decoy and issimilar to what the output from the target would be. This occurs a fewhundred milliseconds after the primer flare ignited and therefore solelythe spectral flare will be burning by the time the spectraldiscriminator of a missile's CCM system will have been activated.

[0047] It can be seen that the spectral flare burns with relativelyconsistent intensity in both bands for a few seconds, more than longenough for the target to be well outside the missile's field of viewwhen the flare finally stops burning.

[0048]FIGS. 4 & 5 show alternative embodiments of a primer flaresuitable for use in decoy flare according to the present invention.Where appropriate like numerals have been used to designate likecomponents.

[0049] Referring to FIG. 4 the primer flare 2 is formed from a singlecylindrical pellet 42 having a central hole 12. The pellet 42 is alsoprovide with a number of other holes 44 which pass through the pellet,the inside surfaces of the central hole 12 and the holes 42 being coatedwith a primer paste to aid in ignition. The use of a single pellet witha number of holes can simplify the production of the primer flare as asingle pellet can be easily machined, however the loss of material fromthe primer flare could necessitate the use of a larger pellet, dependingupon the application.

[0050] For a 47 mm diameter and 40 mm long primer flare made from an MTVcomposition the desired burn rate can be achieved with one central hole12 and five surrounding holes 42, each hole being of 6 mm diameter.Additionally or alternatively transverse holes could be provided downthe length of the primer pellet.

[0051]FIG. 5 shows an a rectangular primer flare 50 comprising a singlepellet with a central hole 52 and a number of grooves 54 running downthe length of the pellet. The grooves may be a few mm thick and about 15mm deep depending upon the application and may be filled with primerpaste to aid ignition.

1. An infra-red emitting decoy flare comprising a flare casing (6), twopyrotechnic components housed within the flare casing and an ignitionmeans (30) for igniting the pyrotechnic components characterised in thatthe two pyrotechnic components comprise a primer flare (2; 50) and aspectral flare (4) wherein the primer flare (2; 50) consists of at leastone primer pellet (8; 42; 52), each primer pellet being composed of afast burning pyrotechnic composition and being adapted such that, inuse, ignition of one primer pellet causes rapid ignition of all theprimer pellets to produce an intense infra-red source, wherein thespectral flare (4) consists of at least one spectral pellet (10), eachspectral pellet being of a pyrotechnic composition adapted such that, inuse, ignition of the spectral pellets produces a spectral infra-redsource wherein the ratio of the intensity of the infra-red spectrum atat least two fixed bands is within a fixed range, and wherein the primerflare (2; 50) and spectral flare (4) are adapted such that, in use, thespectral flare (4) is still burning after the primer flare (2; 50) hasfinished burning.
 2. An infra-red emitting decoy flare as claimed inclaim 1 wherein the spectral flare (4) is adapted such that theintensity of the infra-red radiation emitted, in use, is greater thanthat normally emitted from an intended target.
 3. An infra-red emittingdecoy flare as claimed in claim 1 or claim 2 wherein the primer flare(2) comprises a stack of discs (8) of a pyrotechnic composition.
 4. Aninfra-red emitting decoy flare as claimed in any preceding claim whereinthe primer flare (2) is provided with a central hole (12).
 5. Aninfra-red emitting decoy flare as claimed in any of the preceding claimswherein the primer flare (2) is provided with a plurality of holes (44).6. An infra-red emitting decoy flare as claimed in any of claims 1 to 4wherein the primer flare (50) has a plurality of grooves (54) in itssurface.
 7. An infra-red emitting decoy flare as claimed in anypreceding claim wherein the burn time of the primer flare (2; 50) iswithin the range of 100 to 600 ms.
 8. An infra-red emitting decoy flareas claimed in claim 7 wherein the burn time of the primer flare (2; 50)is in the range of 150 to 250 ms.
 9. An infra-red emitting decoy flareas claimed in any preceding claim wherein the spectral flare (4)comprises a single pellet (10).
 10. An infra-red emitting decoy flare asclaimed in claim 9 wherein the spectral flare (4) is provided with acentral hole (14).
 11. An infra-red emitting decoy flare as claimed inany preceding claim wherein the spectral flare (4) and primer flare (2;50) are adapted such that, in use, the spectral flare is ignited by theburning of the primer flare
 12. An infra-red emitting decoy flare asclaimed in any preceding claim wherein the primer flare (2; 50) isformed from a fast burning magnesium-Teflon-Viton composition.
 13. Aninfra-red emitting decoy flare as claimed in any of claims 1-11 whereinthe primer flare (2; 50) is formed from a pyrotechnic compositionadapted such that, in use, ignition of the primer pellet produces anintense spectral infra-red source wherein the ratio of the intensity ofthe infra-red spectrum at at least two fixed bands is within a fixedrange.
 14. An infra-red emitting decoy flare as claimed in claim 13wherein the primer flare (2; 50) is comprised from a composition ofpotassium benzoate, potassium perchlorate and a binder chosen from thegroup of RDX, HMX or HNS.
 15. An infra-red emitting decoy flare asclaimed in any preceding claim wherein the spectral flare (4) is formedfrom a pyrotechnic composition which produces quantities of gas onignition.
 16. An infra-red emitting decoy flare as claimed in anypreceding claim wherein the spectral flare (4) is formed from acomposition having an organic fuel, an oxidant and a binder.
 17. Aninfra-red emitting decoy flare as claimed in claim 16 wherein theorganic fuel is chosen from the group comprising sucrose, lactose,starch and potassium benzoate.
 18. An infra-red emitting decoy flare asclaimed in any of claims 1 to 15 wherein the spectral flare (4) isformed from a composition having a boron fuel, an oxidant and a binder.19. An infra-red emitting decoy flare as claimed in any of claims 16-18wherein the oxidant is chosen from the group of potassium perchlorate,potassium nitrate, sodium nitrate and ammonium nitrate.
 20. An infra-redemitting decoy flare as claimed in any of claims 16-19 wherein thebinder is chosen from the group of Viton A, dextrin or polybutyl rubber.21. An infra-red emitting decoy flare as claimed in any of claims 16-19wherein the binder is an explosive material having a waxy composition.22. An infra-red emitting decoy flare as claimed in claim 21 wherein thebinder is chosen from the group of RDX, IMX and HNS.
 23. An infra-redemitting decoy flare as claimed in claim 1 wherein the spectral flarecomposition (4) is formed from a mix of 30-40% by mass of potassiumbenzoate and 60-70% by mass of potassium perchlorate together with 3-8%by mass of Viton A, RDX, HMX or HNS.
 24. An infra-red emitting decoyflare as claimed in claim 1 wherein the spectral flare composition (4)is formed from a mix of 30% by mass of boron and 70% by mass ofpotassium nitrate together with a Viton A binder.
 25. An infra-redemitting decoy flare as claimed in any of claim 18 wherein the spectralflare composition (4) comprises an additive such as silicon.
 26. Aninfra-red emitting decoy flare as claimed in claim 25 wherein thespectral flare composition (4) is formed from a mix of 20% by mass ofboron, 10% by mass of silicon and 70% by mass of potassium nitratetogether with a Viton A binder.